Most research on nutrition and human mental development has focused on protein–energy malnutrition (PEM), which consists of deficits in energy and protein as well as other nutrients (Golden 1988). But there is also an extensive literature on the importance to mental development of trace elements and vitamins, as well as the impact of short-term food deprivation. Thus, although the bulk of this essay focuses on PEM and mental development, we begin with an examination of these other areas of concern.
Vitamins and Trace Elements
General Vitamin and Mineral Deficiencies
It is well understood that severe vitamin deficiencies may have drastic effects on mental development. Serious thiamine and niacin deficiencies, for example, as well as those of folic acid and vitamin B12, can cause neuropathy (Carney 1984). But milder, subclinical vitamin deficiencies are much more common, and thus their influence on mental development is presumably of much greater importance. Unfortunately, the extent to which multivitamin and mineral supplements influence intelligence in schoolchildren remains unknown, although this question has been the subject of at least five clinical trials (Schoenthaler 1991).
One study of 90 Welsh children using a multivitamin-mineral supplement over a nine-month period indicated that supplementation produced an increase in nonverbal IQs (Benton and Roberts 1988). A similar study of 410 children in the United States over 13 weeks also revealed an overall increase in nonverbal IQs (Schoenthaler 1991). However, in a Belgian study of 167 children who were supplemented for five months, only boys whose diets had previously been nutritionally deficient showed an increase in verbal IQs (Benton and Buts 1990). Other studies, one in London and the other in Scotland, reported no significant effects of supplementation (Naismith et al. 1988; Crombie et al. 1990).